On the unit group of the Burnside ring for some solvable groups as a biset functor (1710.11218v3)

Abstract: The theory of bisets has been very useful in progress towards settling the longstanding question of determining units for the Burnside ring. In 2006 Bouc used bisets to settle the question for $p$-groups. In this paper, we provide a standard basis for the unit group of the Burnside ring for groups that contain a abelian subgroups of index two. We then extend this result to groups $G$, where $G$ has a normal subgroup, $N$, of odd index, such that $N$ contains an abelian subgroups of index $2$. Next, we study the structure of the unit group of the Burnside ring as a biset functor, $B^\times$ on this class of groups and determine its lattice of subfunctors. We then use this to determine the composition factors of $B^\times$ over this class of groups. Additionally, we give a sufficient condition for when the functor $B^\times$, defined on a class of groups closed under subquotients, has uncountably many subfunctors.